Liquid fuel pumping apparatus

ABSTRACT

A fuel pumping apparatus includes an angularly adjustable cam ring, a piston for effecting angular adjustment, the piston containing a servo-valve which controls the admission of fluid under pressure to one end of a cylinder containing the piston. The servo valve is acted upon by a pressure which varies in accordance with the speed, and it is moved by this pressure against the action of first and section resilient means. Stop means is provided firstly to limit the deflection of the first resilient means and secondly to limit the deflection of the second resilient means.

United States Patent 1 1 Bakti 1 Jan. 21, 1975 [54] LIQUID FUEL PUMPING APPARATUS 3,433,159 3/1969 Kemp 417/219 [75] Inventor: Istvan Bakti, Northolt, England FORElGN PATENTS 0 APPLICATIONS [73] Assignee: C. A. V. Limited, Birmingham, 1,238,283 9/1967 Great Britain 123/139 AQ England 22 F! d: M 1 Primary Examiner-Wil1iam L. Freeh 1 1e ay 1 973 Attorney, Agent, or Firm-Holman & Stern [21] Appl. N0.: 356,131

I o [57] ABSTRACT [30] Foreign Apphcaumi Priority Data A fuel pumping apparatus includes an angularly ad- May 5, 1972 Great Br1ta1n 21014/72 justable cam ring a piston for effecting angular adjust ment, the piston containing a servo-valve which con- 1 1 1 a s 1 1 s s u a [58] Field of Search 417/462, 2 19, 221; acted upon by a pressure which varies in accordance 123/139 139 139 92/122 with the speed, and it is moved by this pressure against the action of first and section resilient means. Stop [56] References Clted means is provided firstly to limit the deflection of the UNITED STATES PATENTS first resilient means and secondly to limit the deflec- 2,910,975 11/1959 Evans 123/139 AQ tion of the second resilient means. 3,051,092 8/1962 Lambeck 417/219 3,394,688 7/1968 Roosa 123/139 A0 3 Claims, 3 Drflwmg Figures LIQUID FUEL PUMPING APPARATUS This invention relates to liquid fuel pumping apparatus for supplying fuel to internal combustion engines and has for its object to provide such an apparatus in a simple and convenient form.

A liquid fuel pumping apparatus in accordance with the invention comprises in combination, an injection pump including a plunger operable by a cam, the injection pump being driven in timed relationship with the engine to which fuel is supplied, a fluid pressure operable piston for controlling the timing of injection of fuel by the injection pump, means for supplying fluid at a pressure which varies in accordance with the speed at which the pump is driven, a servo valve operable to control the application of liquid under pressure to one end of said piston, said servo valve being located within a bore defined in said piston, first and second resilient means acting upon said servo valve to urge the servo valve towards a closed end of the bore, said servo valve contacting the closed end of the bore to urge the piston towards a position in which the timing of injection is fully retarded, passage means through which the fluid under pressure can flow to act on said servo valve in opposition to the force exerted by the resilient means and stop means operable firstly as the pressure of fluid increases, to limit the deflection of said first resilient means and secondly as the pressure of fluid further increases, to limit the deflection of said second resilient means.

Two examples of fuel pumping apparatus in accordance with the invention will now be described with reference to the accompanying drawings in which:

FIGS. 1 and 2 are sectional side elevations through a portion of the apparatus of the two examples respectively, and

FIG. 3 is a diagrammatic arrangement of the apparatus.

With reference to FIG. 3 of the drawings, the apparatus includes a feed pump 7 which supplies fuel under pressure to an injection pump and distributor unit 9 which will be described in greater detail but which includes a timing device 8 also supplied with fuel under pressure. The feed pump 7 includes valve means operable to ensure that the outlet pressure of the feed pump varies in accordance with the speed at which it is driven and there is also provided a regulator 6 which is arranged to provide fuel at a pressure which varies in accordance with the square of the speed at which the apparatus is driven.

Referring to FIG. 1 of the drawings the injection pump and distributor unit includes a body portion 10 in which is journalled a rotary cylindrical distributor member 11 which is driven in timed relationship with an engine with which the apparatus is associated. The distributor member mounts a pair of pumping plungers 12, these being disposed in radially extending bores formed in the distributor member. Surrounding one end of the distributor member is a drive ring 13 in which are formed radially extending slots positioned to correspond with the bores containing the plungers 12. The slots accommodate shoes 14 and at the outer ends of the shoes are mounted rollers 15 which co-operate with the internal periphery of an annular cam ring 16 which is movable angularly within the body 10. The internal periphery of the cam ring defines cam lobes 17 and as the distributor member rotates, inward movement is imparted to the plungers 12 through the interaction of the rollers 15 with the cam lobes 17.

The operation of the apparatus thus far described is well known. During inward movement of the plungers 12 fuel is forced from the inner ends of the bores containing the plungers and is directed to one of a plurality of outlets formed in the body part of the apparatus. When the rollers attain the crests of the cam lobes outward movement is permitted to the plungers under the action of fuel which enters the bore from the outlet of the feed pump 7 under the control of a fuel metering device (not shown). The metering device controls the amount of fuel which is supplied to the inner ends of the bores and thereby determines the quantity of fuel which is supplied at each injection stroke. The rotary part of the aforesaid feed pump is conveniently mounted on the distributor member 11. The angular setting of the cam ring 16 within the body part determines the instant at which fuel is injected to the engine and by varying this setting so the timing of injection of fuel can be varied. The adjustment of the cam ring is achieved by the device 8. The device 8 includes a fluid pressure-operable piston 18 and this is formed with a peg 19 which is accommodated within a suitably shaped slot formed in the cam ring 16. Formed within the piston 18 is a bore 20 which is closed at one end by means of a plug 21. Also accommodated within the bore 20 is a servo valve 22 having a pair of spaced lands. The space intermediate the lands is connected to the outlet of the feed pump 7 through a passage 22a formed in the piston 18 and extending through the body portion 10 whilst the space defined between the left hand land and the plug 21 is connected by way of passage means 23 to the regulator 6 which provides fuel under pressure which varies as the square of the speed at which the distributor member 11 is driven.

The servo valve 22 is loaded into contact with the plug 21 by means of a pair of springs 24, 25. Spring 24 acts intermediate the end of the servo valve remote from the plug 21 and a stop means which is in the form of a top hat sectioned member 26. The spring 25 is located within the member 26 and acts against its base and the end of an end closure 27 secured to the body part. The outwardly directed flange of the member 26 is movable between two limits one of which is defined by the end closure 27 and the other of which is defined by a step defined by the end of the cylinder in which the piston 18 is mounted. The amount by which the member 26 can move is distance A and the amount by which the servo valve must move before it contacts member 26 is referenced R. Moreover, a gap exists which is referenced X, between the end of the piston 18 and the outwardly directed flange of the member 26.

Formed within the piston 18 is a passage 30 which extends from the end of the piston remote from the springs to a port 28 which opens into the bore 20. The port 28 is in the rest condition of the apparatus, covered by the right hand land of the servo valve.

In operation, when the engine is at rest the various parts are in the position shown in H0. 1 and as the engine is cranked a small pressure will be applied to the left hand end of the servo valve 22. This pressure however will be insufficient to overcome the force exerted by the springs 24 and 25, it being understood that the spring 25 exerts a larger force than the spring 24. As the engine speed increases however the pressure acting on the left hand end of the servo valve will increase to the extent that the force exerted by the spring 24 is overcome. When this occurs the servo valve will move towards the right against the action of the spring 24 thereby to open slightly the port 28. With this port opened fuel from the outlet of the feed pump is admitted through the passage 30 and acts upon the left hand end of the piston 18. As a result the piston 18 moves towards the right and an equilibrium position is established. As the speed increases further the servo valve 22 will compress further the spring 24 until a point is reached at which the servo valve contacts the member 26. It will be seen that initially the engine is started with the timing of injection fully retarded and advances as the speed increases. The degree of advance from the rest position is represented by the distance R this of course being a linear distance which must be translated into angular movement of the cam ring 16. As the engine speed further increases a point will be reached at which the force developed by the pressure acting on the servo valve overcomes the effect of the spring 25. When this occurs the member 26 will be moved towards the right and the resulting movement of the servo valve will cause corresponding movement of the piston 18. This continues until the outwardly extending flange of the member 26 contacts the end closure 27. Further movement of the servo valve is therefore prevented and the timing of injection is fully advanced. Thus the further degree of advance is represented by the distance A which of course is a linear distance and which must be converted into degrees of angular movement of the cam ring 16. It is important to note that the distance X should be greater than the distance R otherwise the piston 18 would contact the outwardly turned flange of the member 26, before the servo valve contacted the member 26.

The arrangement which is shown in FIG. 2 is substantially identical with that of FIG. 1 with the exception that the member 26a has its outwardly turned flange accommodated within aspace defined in the end closure member 27a. The extent of movement of the member 26a is represented by A and this corresponds to the distance A in the example of FIG. 1. In this example, however, the extent of movement of the piston 18a is limited by its abutment with the end closure 27a and the extent of movement is represented by the distance R plus A.

I claim:

I. A liquid fuel pumping apparatus comprising in combination, an injection pump including a plunger operable by an adjustable cam, the injection pump being driven in timed relationship with the engine to which fuel is supplied, a fluid pressure operable piston for controlling the timing of injection of fuel by the injection pump, means connecting said piston and said cam whereby movement of the piston will effect adjustment of the cam, means for supplying fluid at a pressure which varies in accordance with the speed at which the pump is driven, a servo valve operable to control the application of liquid under pressure to one end of said piston, said servo valve being located within a bore defined in said piston, first and second resilient means of differing strengths acting upon said servo valve to urge the servo valve towards a closed end of the bore, said servo valve contacting the closed end of the bore to urge the piston towards a position in which the timing of injection is fully retarded, passage means through which fluid under pressure can flow to act on said servo valve in opposition to the force exerted by the resilient means and stop means operable firstly as the pressure of fluid increases, to limit the deflection of said first and weaker resilient means and secondly as the pressure of fluid further increases, to limit the deflection of said second and stronger resilient means.

2. A liquid fuel pumping apparatus comprising in combination, an injection pump including a plunger operable by an adjustable cam, the injection pump being driven in timed relationship with the engine to which fuel is supplied, a fluid pressure operable piston for controlling the timing of injection of fuel by the injection pump, means connecting said piston and said cam whereby movement of the piston will effect adjustment of the cam, means for supplying fluid at a pressure which varies in accordance with the speed at which the pump is driven, a servo valve operable to control the application of liquid under pressure to one end of said piston, said servo valve being located within a bore defined in said piston, first and second resilient means of differing strengths acting upon said servo valve to urge the servo valve towards a closed end of the bore, said servo valve contacting the closed end of the bore to urge the piston towards a position in which the timing of injection is fully retarded, passage means through which fluid under pressure can flow to act on said servo valve in opposition to the force exerted by the resilient means and stop means operable firstly as the pressure of fluid increases, to limit the deflection of said first and weaker resilient means and secondly as the pressure of fluid further increases, to limit the deflection of said second and stronger resilient means, said stop means comprising an axially movable member which is loaded to a first position by the action of said second resilient means and which is movable to a second position against the action of said second resilient means, said first and second positions being determined by spaced stop surfaces engageable with a flange on said axially movable member.

3. An apparatus as claimed in claim 2 in which said axially movable member abuts said first resilient means, said first resilient means being interposed between the servo valve and said member.

4. An apparatus as claimed in claim 3 in which said axially movable member is of hollow form and partly accommodates said second resilient means.

5. An apparatus as claimed in claim 4 in which said servo valve includes a land for controlling flow of fluid through a port defined in the bore of the piston, said port communicating with one end of a cylinder in which the piston is located, the arrangement being such that when fluid under pressure flows through said port into the cylinder, the piston will move to close said port.

6. An apparatus as claimed in claim 5 in which the stop surface which defines said second position of the member is defined by a surface formed on a plug closing one end of said cylinder.

7. An apparatus as claimed in claim 6 in which the stop surface which defines said first position of the member is defined by a stop surface defined at the end of said cylinder adjacent the plug.

8. An apparatus as claimed in claim 6 in which the stop surface which defines said first postion of the member is defined by a further surface formed on said plug, said further surface being disposed intermediate said first mentioned surface and said cylinder. 

1. A liquid fuel pumping apparatus comprising in combination, an injection pump including a plunger operable by an adjustable cam, the injection pump being driven in timed relationship with the engine to which fuel is supplied, a fluid pressure operable piston for controlling the timing of injection of fuel by the injection pump, means connecting said piston and said cam whereby movement of the piston will effect adjustment of the cam, means for supplying fluid at a pressure which varies in accordance with the speed at which the pump is driven, a servo valve operable to control the application of liquid under pressure to one end of said piston, said servo valve being located within a bore defined in said piston, first and second resilient means of differing strengths acting upon said servo valve to urge the servo valve towards a closed end of the bore, said servo valve contacting the closed end of the bore to urge the piston towards a position in which the timing of injection is fully retarded, passage means through which fluid under pressure can flow to act on said servo valve in opposition to the force exerted by the resilient means and stop means operable firstly as the pressure of fluid increases, to limit the deflection of said first and weaker resilient means and secondly as the pressure of fluid further increases, to limit the deflection of said second and stronger resilient means.
 2. A liquid fuel pumping apparatus comprising in combination, an injection pump including a plunger operable by an Adjustable cam, the injection pump being driven in timed relationship with the engine to which fuel is supplied, a fluid pressure operable piston for controlling the timing of injection of fuel by the injection pump, means connecting said piston and said cam whereby movement of the piston will effect adjustment of the cam, means for supplying fluid at a pressure which varies in accordance with the speed at which the pump is driven, a servo valve operable to control the application of liquid under pressure to one end of said piston, said servo valve being located within a bore defined in said piston, first and second resilient means of differing strengths acting upon said servo valve to urge the servo valve towards a closed end of the bore, said servo valve contacting the closed end of the bore to urge the piston towards a position in which the timing of injection is fully retarded, passage means through which fluid under pressure can flow to act on said servo valve in opposition to the force exerted by the resilient means and stop means operable firstly as the pressure of fluid increases, to limit the deflection of said first and weaker resilient means and secondly as the pressure of fluid further increases, to limit the deflection of said second and stronger resilient means, said stop means comprising an axially movable member which is loaded to a first position by the action of said second resilient means and which is movable to a second position against the action of said second resilient means, said first and second positions being determined by spaced stop surfaces engageable with a flange on said axially movable member.
 3. An apparatus as claimed in claim 2 in which said axially movable member abuts said first resilient means, said first resilient means being interposed between the servo valve and said member.
 4. An apparatus as claimed in claim 3 in which said axially movable member is of hollow form and partly accommodates said second resilient means.
 5. An apparatus as claimed in claim 4 in which said servo valve includes a land for controlling flow of fluid through a port defined in the bore of the piston, said port communicating with one end of a cylinder in which the piston is located, the arrangement being such that when fluid under pressure flows through said port into the cylinder, the piston will move to close said port.
 6. An apparatus as claimed in claim 5 in which the stop surface which defines said second position of the member is defined by a surface formed on a plug closing one end of said cylinder.
 7. An apparatus as claimed in claim 6 in which the stop surface which defines said first position of the member is defined by a stop surface defined at the end of said cylinder adjacent the plug.
 8. An apparatus as claimed in claim 6 in which the stop surface which defines said first postion of the member is defined by a further surface formed on said plug, said further surface being disposed intermediate said first mentioned surface and said cylinder. 